Polyurethane foam

ABSTRACT

A polyurethane foam is disclosed having unique load bearing characteristics rendering it suitable for a variety of applications. The foam exhibits high surface-softness and smoothness properties, making it well-suited for use in articles such as pillows and mattress toppers. However, upon continued application of pressure, the resilience of the foam increases sharply, translating into a remarkable support characteristics that make the foam suitable for use in the seat portions of chairs and sofas, as well as in the base portion of mattresses. The foams therefore address the limitations of conventional, high-resilience and visco-elastic polyurethane foams. A process of making the foam and its use in various articles is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing, under 35 U.S.C. §371(c), of International Application No. PCT/CN2018/078261, filed onMar. 7, 2018, which claims priority to United Kingdom Patent ApplicationNo. 1703738.3, filed on Mar. 8, 2017. The entire contents of each of theaforementioned applications are incorporated herein by reference.

INTRODUCTION

The present invention relates to a polyurethane foam, as well as to itsmethod of manufacture and it use in articles and applications requiringcushioning and/or support.

BACKGROUND OF THE INVENTION

Flexible polyurethane foams typically fall into one of three principlecategories. Although conventional foam, high-resilience (HR) foam andvisco-elastic foam (also known as memory foam) are all generally usefulin the bedding and furniture sphere, their individual characteristicsrenders each foam particularly suited to certain applications. Owing toits flexibility and support properties, conventional foam, istraditionally used in the back portion of seats and chairs, as well asthe base portion of mattresses. HR foam, offering good body support andresilience, is well-suited for use in the seat portion of seats, chairsand sofas. Visco-elastic is typically used in the manufacture ofpillows, the upper portion of mattresses and in mattress toppers, whereits shape-conforming, energy-attenuating and sound dampening propertiesare particularly advantageous.

In spite of the usefulness of conventional, HR and visco-elastic foams,there exist numerous applications for which it would be advantageous tocombine the benefits of multiple foam types. Efforts to address thisneed by combining two or more foam types into a given article—forexample in discrete laminated layers—have proved unsuccessful, owing inpart to the resulting composite foam exhibiting undesirable propertiesat the interface of the individual foams.

There is therefore a need for a new type of foam that combines theadvantages of conventional, HR and visco-elastic foams into a singlematerial. In addition, in order to maximize the applicability of thematerial across multiple applications, there is an ongoing need for afoam that exhibits other advantageous properties, such as high sag valueand increased surface softness and smoothness.

The present invention was devised with the foregoing in mind.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided aprocess for the preparation of a polyurethane foam, the processcomprising/consisting essentially of/consisting of the steps of:

-   -   a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 72-110,        -   iii. at least one surfactant in an amount of 0.4-1.0 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.6 per            hundred parts polyol,        -   v. water in an amount of 1.5-4.0 per hundred parts polyol,            and        -   vi. optionally at least one flame retardant in an amount of            4.0-15.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).

According to a second aspect of the present invention there is provideda polyurethane foam obtainable, obtained or directly obtained by theprocess according to the first aspect of the invention.

According to a third aspect of the present invention there is provided apolyurethane foam having a sag value of 2.8-3.5, wherein the sag valueis calculated according to the following expression:

${{Sag}{value}} = \frac{{IFD}65\%}{{IFD}25\%}$and wherein IFD65% and IFD25% values are determined according to theprotocol set forth in ISO 2439:2008.

According to a fourth aspect of the present invention there is providedan article comprising a polyurethane foam according to the second orthird aspect of the invention.

According to a further aspect of the present invention there is provideda process for the preparation of a polyurethane foam, the processcomprising/consisting essentially of/consisting of the steps of:

-   -   a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 65-90,        -   iii. at least one surfactant in an amount of 0.4-1.0 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.1-0.6 per            hundred parts polyol, and        -   v. water in an amount of 1.5-4.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).

DETAILED DESCRIPTION OF THE INVENTION

Preparation of Polyurethane Foam

As described hereinbefore, the present invention provides a process forthe preparation of a polyurethane foam, the process comprising the stepsof:

-   -   a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 72-110,        -   iii. at least one surfactant in an amount of 0.4-1.0 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.6 per            hundred parts polyol,        -   v. water in an amount of 1.5-4.0 per hundred parts polyol,            and        -   vi. optionally at least one flame retardant in an amount of            4.0-15.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).

Against the backdrop of conventional, HR and visco-elastic flexiblepolyurethane foams, the present inventor has now devised a process thatsurprisingly allows the benefits of each of these foams to be combinedinto a single new flexible polyurethane foam. In particular, foamsobtainable by the present process combine the support andpressure-reducing characteristics of conventional, HR and visco-elasticfoam, whilst simultaneously offering noticeably improved surfacesmoothness and softness. Such characteristics are attributable, at leastin part, to the unique load-bearing properties of those foams obtainableby the present process. In particular, the present process results infoams that exhibit a high degree of surface softness and smoothness uponinitial application of pressure to the foam's surface. However, uponcontinued application of pressure, the foam's resistance to compressionincreases sharply, thus offering increased resilience and support. As aconsequence, the foams obtainable by the present process are not onlywell-suited to applications requiring robust support, such as in seatsand mattress bases, but are equally useful in articles that are intendedto be pleasing to the touch, such as mattress surfaces and mattresstoppers.

Optionally, those ingredients mixed in step a) comprise at least oneflame retardant in an amount of 4.0-15.0 per hundred parts polyol. Theresulting foams exhibit BS5852 Crib5 fire retardancy. BS5852 Crib5 fireretardancy is a UK requirement which is perhaps the most stringent ofall international flame retardancy standards. Achieving highsurface-softness, high sag value and BS5852 crib 5 compliance in asingle polyurethane foam is particularly advantageous.

In an embodiment, the ingredients specified in step a) are mixed at aspeed of 2,000-8,000 rpm. Suitably, the ingredients specified in step a)are mixed at a speed of 4,000-6,000 rpm.

In an embodiment, the polyol, which is suitably a polyether polyol, hasan average molecular weight of 7,000-9,000 Da. Suitably, the polyol hasan average molecular weight of 7,500-8,500 Da.

In an embodiment, the polyol has an OH functionality of 2.5-3.5. The OHfunctionality describes the average number of OH groups in a molecule ofpolyol, and can be calculated according to the following expression:

${{OH}{functionality}} = \frac{{total}{moles}{OH}}{{total}{moles}{polyol}}$Suitably, the polyol has an OH functionality of 2.8-3.2.

In an embodiment, the polyol has an OH value of 20-48. The OH value(also known as OH number) is the milligrams of potassium hydroxideequivalent to the hydroxyl content in one gram of polyol, and can becalculated according to the following expression:

${{OH}{value}} = \frac{56100*{OH}{functionality}}{{equivalent}{weight}{of}{polyol}}$Suitably, the polyol has an OH value of 23-33. More suitably, the polyolhas an OH value of 26-30.

Suitably, only one polyol (e.g. a polyether polyol) is used in step a).

In an embodiment, the methylene diphenyl diisocyanate has an NCO contentof 28-33%. The NCO content (expressed as a percentage) describes theweight percentage of NCO groups in an isocyanate-containing material.Suitably, the methylene diphenyl diisocyanate has an NCO content of29-32%. More suitably, the methylene diphenyl diisocyanate has an NCOcontent of 29-31%. Most suitably, the methylene diphenyl diisocyanatehas an NCO content of 29-30.5%.

Suitably, methylene diphenyl diisocyanate is the only isocyanate used instep a).

In an embodiment, the methylene diphenyl diisocyanate is a modifiedmethylene diphenyl diisocyanate.

In an embodiment, the methylene diphenyl diisocyanate has a density at25° C. of 1.0-1.4 g cm⁻³. More suitably, the methylene diphenyldiisocyanate has a density at 25° C. of 1.1-1.3 g cm⁻³.

In an embodiment, the methylene diphenyl diisocyanate has a viscosity at25° C. of 45-85 mPa s. Suitably, the methylene diphenyl diisocyanate hasa viscosity at 25° C. of 55-75 mPa s. More suitably, the methylenediphenyl diisocyanate has a viscosity at 25° C. of 60-70 mPa s.

In an embodiment, the methylene diphenyl diisocyanate has a flash point(according to the Cleveland Cup ASTM method D92) at 25° C. of 180-230°C. Suitably, the methylene diphenyl diisocyanate has a flash point at25° C. of 195-215° C.

In an embodiment, the methylene diphenyl diisocyanate is a modifiedmethylene diphenyl diisocyanate having a density at 25° C. of 1.1-1.3gcm⁻³, a viscosity at 25° C. of 55-75 mPa s, and a flash point at 25° C.of 195-215° C.

In an embodiment, the amount of methylene diphenyl diisocyanate relativeto the amount of polyol is sufficient to give an ISO index of 73-105.Suitably, the amount of methylene diphenyl diisocyanate relative to theamount of polyol is sufficient to give an ISO index of 80-103. Moresuitably, the amount of methylene diphenyl diisocyanate relative to theamount of polyol is sufficient to give an ISO index of 85-100. Even moresuitably, the amount of methylene diphenyl diisocyanate relative to theamount of polyol is sufficient to give an ISO index of 87-95. Mostsuitably, the amount of methylene diphenyl diisocyanate relative to theamount of polyol is sufficient to give an ISO index of 88-92.

In another embodiment, the amount of methylene diphenyl diisocyanaterelative to the amount of polyol is sufficient to give an ISO index of70-80. Alternatively, the amount of methylene diphenyl diisocyanaterelative to the amount of polyol is sufficient to give an ISO index of73-78.

Any surfactant suitable for use in the preparation of a polyurethanefoam may be used. Suitable surfactants are well known to the skilledperson, and include polydimethylsiloxane-polyoxyalkylene blockcopolymers, silicone oils and nonylphenol ethoxylates. Suitably, thesurfactant is a silicone oil.

In an embodiment, in step a), the surfactant is present in an amount of0.4-0.8 per hundred parts polyol. Suitably, in step a), the surfactantis present in an amount of 0.5-0.8 per hundred parts polyol. Moresuitably, the surfactant is present in an amount of 0.5-0.75 per hundredparts polyol. Most suitably, in step a), the surfactant is present in anamount of 0.55-0.75 per hundred parts polyol.

Alternatively, in step a), the surfactant is present in an amount of0.45-0.65 per hundred parts polyol.

In an embodiment, the amine catalyst is suitable for enhancing thenucleophilicity of the polyol. Suitable amine catalysts includetriethylenediamine (TEDA), dimethylcyclohexylamine (DMCHA), triethylenediamine, bis(2-dimethyl amino ethyl)ether (BDE) and dimethylethanolamine(DMEA). Most suitably, the catalyst is triethylene diamine.

In an embodiment, in step a), the amine catalyst is present in an amountof 0.2-0.55 per hundred parts polyol. Suitably, in step a), the aminecatalyst is present in an amount of 0.45-0.55 per hundred parts polyol.

Alternatively, in step a), the amine catalyst is present in an amount of0.2-0.4 or 0.25-0.35 per hundred parts polyol.

In an embodiment, in step a), water is present in an amount of 1.5-3.5per hundred parts polyol. Suitably, in step a), water is present in anamount of 1.5-3.3 per hundred parts polyol. More suitably, in step a),water is present in an amount of 1.75-2.8 per hundred parts polyol. Mostsuitably, in step a), water is present in an amount of 1.75-2.5 perhundred parts polyol.

Alternatively, in step a), water is present in an amount of 2.0-3.5 perhundred parts polyol. Suitably, in step a), water is present in anamount of 2.5-3.5 per hundred parts polyol. More suitably, in step a),water is present in an amount of 2.9-3.3 per hundred parts polyol

In an embodiment, the flame retardant is present in an amount of5.0-14.0 per hundred parts polyol. More suitably, the flame retardant ispresent in an amount of 6.5-14.0 per hundred parts polyol. Moresuitably, the flame retardant is present in an amount of 8.0-13.5 perhundred parts polyol. Even more suitably, the flame retardant is presentin an amount of 10.0-13.0 per hundred parts polyol.

Alternatively, the flame retardant is present in an amount of 4.0-10.0per hundred parts polyol. Suitably, the flame retardant is present in anamount of 6.0-8.0 per hundred parts polyol.

When included in step a), the flame retardant may be a chlorinatedphosphate ester, a halogen-free phosphate ester, or a mixture thereof.

When included in step a), the flame retardant may be used in conjunctionwith a flame-retardant synergist. Suitably, the synergist is present inan amount of 8.0-20.0 per hundred parts polyol. More suitably, thesynergist is present in an amount of 9.0-17.0 per hundred parts polyol.Most suitably, the synergist is present in an amount of 13.0-16.0 perhundred parts polyol.

Alternatively, the synergist is present in an amount of 8.0-15.0 perhundred parts polyol. Suitably, the synergist is present in an amount of8.0-12.0 per hundred parts polyol.

The synergist may be melamine or melamine-based.

In an embodiment, those ingredients mixed in step a) further comprise atleast one tin catalyst in an amount of 0.01-0.2. Suitably, thoseingredients mixed in step a) further comprise at least one tin catalystin an amount of 0.01-0.1 per hundred parts polyol. More suitably, thoseingredients mixed in step a) further comprise at least one tin catalystin an amount of 0.01-0.05 per hundred parts polyol.

When included in step a), any tin catalyst suitable for use in thepreparation of a polyurethane foam may be used. Suitable tin catalystsare well known to the skilled person, and include dibutyltindioctanoate, dibutyltin dilaurate and tin alkyl carboxylates (eg.stannous octoate). In an embodiment, the tin catalyst is a mild Lewisacid. Suitably, the tin catalyst is a tin alkyl carboxylate (e.g.stannous octoate).

In an embodiment, those ingredients mixed in step a) further comprise atleast one of a chain extender and a cross-linker in an amount of 0.2-1.5per hundred parts polyol. Suitably, those ingredients mixed in step a)further comprise at least one of a chain extender and a cross-linker inan amount of 0.5-0.9 per hundred parts polyol.

Alternatively, those ingredients mixed in step a) further comprise atleast one of a chain extender and a cross-linker in an amount of 0.6-1.2per hundred parts polyol.

When included in step a), any chain extender and/or cross linkersuitable for use in the preparation of a polyurethane foam may be used.Suitable chain extenders and/or cross linkers are well known to theskilled person, and include ethylene glycol, 1,4-butanediol, ethanolamine and diethanol amine. In an embodiment, the chain extender and/orcross linker is diethanol amine.

In an embodiment, those ingredients mixed in step a) further comprise atleast one cell opener in an amount of 1.0-6.0 per hundred parts polyol.Suitably, those ingredients mixed in step a) further comprise at leastone cell opener in an amount of 2.0-5.5 per hundred parts polyol.

When included in step a), any cell opener suitable for use in thepreparation of a polyurethane foam may be used. Suitable cell openersare well known to the skilled person, and include silicone-basedcompounds and polyol-based compounds. In an embodiment, the cell openeris a polyol-based compound.

In an embodiment, those ingredients mixed in step a) further comprise atleast one blowing agent in an amount of 1.0-10.0 per hundred partspolyol. Considering that the presence of water in step a) is mandatory(which reacts with the isocyanate to produce CO2), the presence of adedicated blowing agent is optional. Suitably, those ingredients mixedin step a) further comprise at least one blowing agent in an amount of1.5-8.0 per hundred parts polyol.

Alternatively, those ingredients mixed in step a) further comprise atleast one blowing agent in an amount of 6.0-8.0 per hundred partspolyol.

When included in step a), any blowing agent suitable for use in thepreparation of a polyurethane foam may be used. Suitable blowing agentsare well known to the skilled person, and include that materials thatare capable of absorbing heat from the exothermic reactions, vaporizingand providing additional gas useful in expanding the foam to a lowerdensity. In an embodiment, the blowing agent is methylene chloride.

In an embodiment, those ingredients mixed in step a) further comprise apigment.

In an embodiment, in step b), the mixture resulting from step a) iscured in an atmosphere of air.

In an embodiment, in step b), the mixture resulting from step a) iscured at a temperature of 15-40° C.

In an embodiment, in step b), the mixture resulting from step a) iscured at a pressure of 0.9 to 1.1 bar.

In an embodiment, in step b), the foam is cured for 24-120 hours.Suitably, in step b), the foam is cured for 48-96 hours.

In an embodiment, the process is continuous (as opposed to a batch ordiscontinuous process). Suitably, foam is formed at a speed of 3-5m/min.

In an embodiment, in step a), the polyol is fed to a mixer at a rate of100-140 kg/min. Suitably, in step a), the polyol is fed to a mixer at arate of 110-130 kg/min.

In an embodiment, in step a), the methylene diphenyl diisocyanate is fedto a mixer at a rate of 30-80 kg/min. Suitably, in step a), themethylene diphenyl diisocyanate is fed to a mixer at a rate of 40-60kg/min.

In an embodiment, in step a), the surfactant is fed to a mixer at a rateof 45-85 kg/min. Suitably, in step a), the surfactant is fed to a mixerat a rate of 55-75 kg/min.

In an embodiment, in step a), the amine catalyst is fed to a mixer at arate of 20-50 kg/min. Suitably, in step a), the amine catalyst is fed toa mixer at a rate of 30-40 kg/min.

In an embodiment, in step a), water is fed to a mixer at a rate of 2-6kg/min. Suitably, in step a), water is fed to a mixer at a rate of 3-5kg/min.

In an embodiment, when it features in step a), the flame retardant isfed to a mixer at a rate of 5-12 kg/min. Suitably, when it features instep a), the flame retardant is fed to a mixer at a rate of 7-10 kg/min.

In an embodiment, when it features in step a), the flame retardantsynergist is fed to a mixer at a rate of 8-16 kg/min. Suitably, when itfeatures in step a), the flame retardant synergist is fed to a mixer ata rate of 10-14 kg/min.

In an embodiment, when it features in step a), the blowing agent is fedto a mixer at a rate of 5-12 kg/min. Suitably, when it features in stepa), the blowing agent is fed to a mixer at a rate of 7-10 kg/min.

In an embodiment, when it features in step a), the tin catalyst is fedto a mixer at a rate of 0.01-0.07 kg/min. Suitably, when it features instep a), the tin catalyst is fed to a mixer at a rate of 0.025-0.055kg/min.

In an embodiment, when it features in step a), the cell opener is fed toa mixer at a rate of 1-6 kg/min. Suitably, when it features in step a),the cell opener is fed to a mixer at a rate of 2.5-4.5 kg/min.

In an embodiment, when it features in step a), the chain extender and/orcross linker is fed to a mixer at a rate of 0.1-3.0 kg/min. Suitably,when it features in step a), the chain extender and/or cross linker isfed to a mixer at a rate of 0.5-1.5 kg/min.

In an embodiment, the ingredients specified in step a) are mixed at apressure of 0.2-0.4 mPa.

In an embodiment, the process is as defined in any one of numberedparagraphs (1)-(30):

-   -   1) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.6 per            hundred parts polyol,        -   v. water in an amount of 1.5-4.0 per hundred parts polyol,            and        -   vi. optionally at least one flame retardant in an amount of            4.0-15.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   2) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 72-110,        -   iii. at least one surfactant in an amount of 0.4-1.0 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. water in an amount of 1.5-3.3 per hundred parts polyol,            and        -   vi. optionally at least one flame retardant in an amount of            4.0-15.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   3) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. water in an amount of 1.5-3.3 per hundred parts polyol,            and        -   vi. optionally at least one flame retardant in an amount of            4.0-15.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   4) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. water in an amount of 1.5-3.3 per hundred parts polyol,            and        -   vi. at least one flame retardant in an amount of 4.0-15.0            per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   5) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. water in an amount of 1.5-3.3 per hundred parts polyol,            and        -   vi. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   6) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vi. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   vii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   7) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.2 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   8) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   9) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one of a chain extender and a cross-linker in an            amount of 0.2-1.5 per hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   10) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one of a chain extender and a cross-linker in an            amount of 0.5-0.9 per hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   11) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one cell opener in an amount of 1.0-6.0 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   12) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   13) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one blowing agent in an amount of 1.0-10.0 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   14) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   vi. water in an amount of 1.5-3.3 per hundred parts polyol,        -   vii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   viii. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   15) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one blowing agent in an amount of 1.0-10.0 per            hundred parts polyol,        -   vi. at least one cell opener in an amount of 1.0-6.0 per            hundred parts polyol,        -   vii. water in an amount of 1.5-3.3 per hundred parts polyol,        -   viii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   ix. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   16) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   vi. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   vii. water in an amount of 1.5-3.3 per hundred parts polyol,        -   viii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   ix. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   17) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.2 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.2-1.5 per hundred parts polyol,        -   vii. water in an amount of 1.5-3.3 per hundred parts polyol,        -   viii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   ix. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   18) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. water in an amount of 1.5-3.3 per hundred parts polyol,        -   viii. at least one flame retardant in an amount of 6.5-14.0            per hundred parts polyol, and        -   ix. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   19) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.2 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.2-1.5 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.0-10.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 1.0-6.0 per            hundred parts polyol,        -   ix. water in an amount of 1.5-3.3 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 6.5-14.0 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   20) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.5-3.3 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 6.5-14.0 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            8.0-20.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   21) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-105,        -   iii. at least one surfactant in an amount of 0.5-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.55 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.5-3.3 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 6.5-14.0 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            9.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   22) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 87-95,        -   iii. at least one surfactant in an amount of 0.55-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.45-0.55            per hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.75-2.8 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 8.0-13.5 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            9.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   23) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 87-95,        -   iii. at least one surfactant in an amount of 0.55-0.8 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.45-0.55            per hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.75-2.6 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 8.0-13.5 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            9.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   24) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.75 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.45-0.55            per hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.1 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.75-2.5 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 10.0-13.0            per hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            13.0-16.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   25) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.85 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.45-0.55            per hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.6 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.5-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.5-8.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.75-2.5 per hundred parts polyol,        -   x. optionally at least one flame retardant in an amount of            10.0-13.0 per hundred parts polyol, and        -   xi. optionally at least one flame retardant synergist in an            amount of 13.0-16.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   26) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 73-77,        -   iii. at least one surfactant in an amount of 0.45-0.65 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.2-0.4 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.01-0.05 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.7-0.9 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 5.0-9.0 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 3.0-3.4 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 5.0-9.0 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            8.0-12.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   27) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.85 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.4-0.6 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.03-0.07 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.45-0.75 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 3.5-7.5 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.8-2.2 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 2.0-4.0 per            hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            13.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   28) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.85 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.4-0.6 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.03-0.07 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.45-0.75 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 3.5-7.5 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 3.8-4.0 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 10.5-13.5            per hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            13.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   29) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.85 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.4-0.6 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.03-0.07 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.45-0.75 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 3.5-7.5 per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 2.0-5.5 per            hundred parts polyol,        -   ix. water in an amount of 1.8-2.0 per hundred parts polyol,        -   x. at least one flame retardant in an amount of 10.5-13.5            per hundred parts polyol, and        -   xi. at least one flame retardant synergist in an amount of            13.0-17.0 per hundred parts polyol;    -   b) curing the mixture resulting from step a).    -   30) a) mixing together the following ingredients in the amounts        specified:        -   i. at least one polyol having an average molecular weight of            6,000-12,000 Da, wherein the polyol has an OH functionality            of 2-4,        -   ii. at least one methylene diphenyl diisocyanate having an            NCO content of 26-33%, wherein the amount of diisocyanate            relative to the amount of polyol is sufficient to give an            ISO index of 88-92,        -   iii. at least one surfactant in an amount of 0.55-0.85 per            hundred parts polyol,        -   iv. at least one amine catalyst in an amount of 0.4-0.6 per            hundred parts polyol,        -   v. at least one tin catalyst in an amount of 0.03-0.07 per            hundred parts polyol,        -   vi. at least one of a chain extender and a cross-linker in            an amount of 0.45-0.75 per hundred parts polyol,        -   vii. at least one blowing agent in an amount of 1.0-per            hundred parts polyol,        -   viii. at least one cell opener in an amount of 4.5-5.5 per            hundred parts polyol, and        -   ix. water in an amount of 1.8-2.0 per hundred parts polyol,    -   b) curing the mixture resulting from step a).

In any of the numbered paragraphs (1)-(30), the polyol, methylenediphenyl diisocyanate, surfactant, amine catalyst, water, flameretardant, flame retardant synergist, tin catalyst, chain extender/crosslinker, cell opener and/or blowing agent may have any of the definitionsrecited hereinbefore.

In an embodiment, in any of the numbered paragraphs (1)-(30), thepolyol, which is suitably a polyether polyol, has a molecular weight of7,000-9,000 Da or 7,500-8,500 Da. Suitably, the polyol has a molecularweight of 7,000-9,000 Da or 7,750-8,250 Da.

In an embodiment, in any of the numbered paragraphs (1)-(30), the polyolhas an OH value of 20-48 or 26-30.

In an embodiment, in any of the numbered paragraphs (1)-(30), only onepolyol is provided in step a).

In an embodiment, in any of the numbered paragraphs (1)-(30), the polyolhas a molecular weight of 7,500-8,500 Da and an OH value of 26-30.

In an embodiment, in any of the numbered paragraphs (1)-(30), themethylene diphenyl diisocyanate has an NCO content of 28-33% or 29-32%.Suitably, the methylene diphenyl diisocyanate has an NCO content of29-31%. Most suitably, the methylene diphenyl diisocyanate has an NCOcontent of 29-30.5%.

In an embodiment, in any of the numbered paragraphs (1)-(30), themethylene diphenyl diisocyanate is a modified methylene diphenyldiisocyanate having a density at 25° C. of 1.1-1.3 gcm⁻³, a viscosity at25° C. of 55-75 mPa s, and a flash point at 25° C. of 195-215° C.

In an embodiment, in any of the numbered paragraphs (1)-(30), themethylene diphenyl diisocyanate is the only isocyanate used in step a).

In an embodiment, in any of the numbered paragraphs (1)-(30), thesurfactant is a silicone oil.

In an embodiment, in any of the numbered paragraphs (1)-(30), the aminecatalyst is suitable for enhancing the nucleophilicity of the polyol.

In an embodiment, in any of the numbered paragraphs (1)-(30), the flameretardant is a chlorinated phosphate ester, a halogen-free phosphateester, or a mixture thereof.

In an embodiment, in any of the numbered paragraphs (1)-(30), the flameretardant synergist is melamine or melamine-based.

In an embodiment, in any of the numbered paragraphs (1)-(30), the tincatalyst is a tin alkyl carboxylate.

In an embodiment, in any of the numbered paragraphs (1)-(30), the chainextender and/or cross linker is selected from ethylene glycol,1,4-butanediol, ethanol amine and diethanol amine.

In an embodiment, in any of the numbered paragraphs (1)-(30), the cellopener is a polyol-based compound.

In an embodiment, in any of the numbered paragraphs (1)-(30), theblowing agent is methylene chloride.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48, and the methylene diphenyl diisocyanate has an NCO content of28-33%.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da and an OH value of20-48, and

the methylene diphenyl diisocyanate has an NCO content of 29-32%.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da and an OH value of26-30, and

the methylene diphenyl diisocyanate has an NCO content of 29-32%.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da and an OH value of26-30, and

the methylene diphenyl diisocyanate is a modified methylene diphenyldiisocyanate having a density at 25° C. of 1.1-1.3 gcm⁻³, a viscosity at25° C. of 55-75 mPa s, a flash point at 25° C. of 195-215° C., and anNCO content of 29-32%.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%, and

the surfactant is a silicone oil.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil, and

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol, and

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof, and

the flame retardant synergist is melamine or melamine-based.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based, and tincatalyst is a tin alkyl carboxylate.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based,

tin catalyst is a tin alkyl carboxylate, and

the chain extender and/or cross linker is selected from ethylene glycol,1,4-butanediol, ethanol amine and diethanol amine.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,000-9,000 Da and an OH value of20-48,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based,

tin catalyst is a tin alkyl carboxylate,

the chain extender and/or cross linker is selected from ethylene glycol,1,4-butanediol, ethanol amine and diethanol amine,

the cell opener is a polyol-based compound, and

the blowing agent is methylene chloride.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%, and

the surfactant is a silicone oil.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil, and

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol, and

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof, and

the flame retardant synergist is melamine or melamine-based.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based, and

tin catalyst is a tin alkyl carboxylate.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based,

tin catalyst is a tin alkyl carboxylate, and

the chain extender and/or cross linker is selected from ethylene glycol,1,4-butanediol, ethanol amine and diethanol amine.

In an embodiment, in any of the numbered paragraphs (1)-(30),

the polyol has a molecular weight of 7,500-8,500 Da (or 7,250-8,250 Da)and an OH value of 26-30,

the methylene diphenyl diisocyanate has an NCO content of 29-32%,

the surfactant is a silicone oil,

the amine catalyst is suitable for enhancing the nucleophilicity of thepolyol,

the flame retardant is a chlorinated phosphate ester, a halogen-freephosphate ester, or a mixture thereof,

the flame retardant synergist is melamine or melamine-based,

tin catalyst is a tin alkyl carboxylate,

the chain extender and/or cross linker is selected from ethylene glycol,1,4-butanediol, ethanol amine and diethanol amine,

the cell opener is a polyol-based compound, and

the blowing agent is methylene chloride.

In any of the embodiments based on numbered paragraphs (1)-(30), theingredients specified in step a) are mixed at a speed of 2,000-8,000rpm, preferably 4,000-6,000 rpm.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepa), the polyol, methylene diphenyl diisocyanate, surfactant, aminecatalysts, water, flame retardant, flame retardant synergist, blowingagent, tin catalyst, cell opener and/or chain extender/cross linker maybe fed to a mixer at any of the rates specified hereinbefore.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepa),

the polyol is fed to a mixer at a rate of 100-140 kg/min, and

the methylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80kg/min.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepa),

the polyol is fed to a mixer at a rate of 100-140 kg/min,

the methylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80kg/min,

the surfactant is fed to a mixer at a rate of 45-85 kg/min,

the amine catalyst is fed to a mixer at a rate of 20-50 kg/min, and

water is fed to a mixer at a rate of 2-6 kg/min.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepa),

the polyol is fed to a mixer at a rate of 100-140 kg/min,

the methylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80kg/min,

the surfactant is fed to a mixer at a rate of 45-85 kg/min,

the amine catalyst is fed to a mixer at a rate of 20-50 kg/min,

water is fed to a mixer at a rate of 2-6 kg/min, and

the flame retardant is fed to a mixer at a rate of 5-12 kg/min.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepa),

the polyol is fed to a mixer at a rate of 100-140 kg/min,

the methylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80kg/min,

the surfactant is fed to a mixer at a rate of 45-85 kg/min,

the amine catalyst is fed to a mixer at a rate of 20-50 kg/min,

water is fed to a mixer at a rate of 2-6 kg/min,

the flame retardant is fed to a mixer at a rate of 5-12 kg/min,

the flame retardant synergist is fed to a mixer at a rate of 8-16kg/min,

the blowing agent is fed to a mixer at a rate of 5-12 kg/min,

tin catalyst is fed to a mixer at a rate of 0.01-0.07 kg/min,

the cell opener is fed to a mixer at a rate of 1-6 kg/min, and

the chain extender and/or cross linker is fed to a mixer at a rate of0.1-3.0 kg/min.

In any of the embodiments based on numbered paragraphs (1)-(30), in stepb), the mixture resulting from step a) is cured in an atmosphere of airat a temperature of 15-40° C.

Polyurethane Foam

As described hereinbefore, the present invention provides a polyurethanefoam obtainable by the process according to the first aspect of theinvention.

As described hereinbefore, the present invention provides a polyurethanefoam having a sag value of 2.8-3.5, wherein the sag value is calculatedaccording to the following expression:

${{Sag}{value}} = \frac{{IFD}65\%}{{IFD}25\%}$and wherein IFD65% and IFD25% values are determined according to theprotocol set forth in ISO 2439:2008.

The flexible polyurethane foams of the present invention offer a varietyof surprising advantages over known polyurethane foams. Perhaps mostnotably, the present invention has allowed certain desirable propertiesexhibited across conventional, HR and visco-elastic flexiblepolyurethane foams to be brought together into a single polyurethanefoam. In particular, the foams of the present invention combine thesupport and pressure-reducing characteristics of conventional, HR andvisco-elastic foam, whilst simultaneously offering noticeably improvedsurface smoothness and softness. Such characteristics are attributable,at least in part, to the unique load bearing properties of the foams ofthe present invention. In particular, the present foams exhibit a highdegree of surface softness and smoothness upon initial application ofpressure to the foam's surface. However, upon continued application ofpressure, the foam's resistance to compression increases sharply, thusoffering increased resilience and support. As a consequence, the presentfoams are not only well-suited to applications requiring robust support,such as in seats and mattress bases, but are equally useful in articlesthat are intended to be pleasing to the touch, such as mattress surfacesand mattress toppers.

The following paragraphs are applicable to the polyurethane foams ofboth the second and third aspects of the invention.

The polyurethane foam has a sag value of 2.8-3.5. The sag value is aparameter commonly used in the foam industry to describe the loadbearing characteristics of a given foam. With this industry, the sagvalue is calculated according to the following expression:

${{Sag}{value}} = \frac{{IFD}65\%}{{IFD}25\%}$

IFD (indentation force deflection, previously indentation loaddeflection) is one test method to determine the load bearingcharacteristics (firmness or stiffness) of a foam, and is expressed inNewtons at a given percent deflection of the foam. To obtain the IFD25%value, a 200 mm diameter flat circular indenter plate is driven into asquare foam sample (380 mm side length, 50 mm thickness), stopping whenit reaches a deflection of 12.5 mm (25% of the 50 mm thickness). Thetesting device records the force required to hold this foam indented for30 seconds. The higher the force reading, the higher the load bearingcapacity of the foam. The ISO Standard entitled “Flexible cellularpolymeric materials—Determination of hardness (indentation technique)(ISO 2439:2008) English version of DIN EN ISO 2439:2009-05” (referred togenerally herein as ISO 2439:2008) provides further details of how IFDand sag value are calculated at paragraph 7.4 Method B.

The sag value (also known as sag factor or compressive deflectioncoefficient) is the ratio of the IFD65% value to the IFD25% value and isexpressed in real numbers with one decimal. The sag value gives anindication of cushioning quality, and a high value indicates aresistance to “bottoming out.” The sag value properties of the presentfoams reflects the advantageous load bearing properties discussed above.

In an embodiment, the polyurethane foam has a sag value of 3.0-3.5.Suitably, the polyurethane foam has a sag value of 3.1-3.4. Moresuitably, the polyurethane foam has a sag value of 3.2-3.4.

In an embodiment, the polyurethane foam has an IFD25% value of 10-40.Suitably, the polyurethane foam has an IFD25% value of 20-30.

In an embodiment, the polyurethane foam has an IFD40% value of 33-80.Suitably, the polyurethane foam has an IFD40% value of 40-70. Moresuitably, the polyurethane foam has an IFD40% value of 40-55.

Alternatively, polyurethane foam has an IFD40% value of 20-50. Suitably,the polyurethane foam has an IFD40% value of 30-40.

In an embodiment, the polyurethane foam has an IFD65% value of 50-115.Suitably, the polyurethane foam has an IFD65% value of 50-100. Moresuitably, the polyurethane foam has an IFD65% value of 70-95. Mostsuitably, the polyurethane foam has an IFD65% value of 72-85.

Alternatively, the polyurethane foam has an IFD65% value of 60-90.Suitably, the polyurethane foam has an IFD65% value of 65-75.

In an embodiment, the polyurethane foam has a density of 35-60 kg/m³.Suitably, the polyurethane foam has a density of 40-60 kg/m³. Moresuitably, the polyurethane foam has a density of 40-55 kg/m³. Even moresuitably, the polyurethane foam has a density of 45-50 kg/m³.

In an embodiment, the polyurethane foam has a ball resilience of >60%(e.g. 60-72%). Ball resilience was tested according to the protocoloutlined in ISO standard 8307:1990(E). The test pieces were conditionedand tested at a temperature of 23±2° C. and a humidity of 55±10%.

In an embodiment, the polyurethane foam comprises a polyurethane formedby the reaction of at least one polyol having a molecular weight of6,000-12,000 Da and an OH functionality of 2-4 with at least onemethylene diphenyl diisocyanate having an NCO content of 26-33%. Thepolyol and methylene diphenyl diisocyanate may have any one or more ofthose definitions discussed in respect of the first aspect of theinvention.

In an embodiment, the polyurethane foam comprises one or more of achlorinated phosphate ester and a halogen-free phosphate ester fireretardant, or a residue thereof.

In an embodiment, the polyurethane foam exhibits BS5852 Crib5 fireretardancy. BS5852 Crib5 fire retardancy is a UK requirement which isperhaps the most stringent of all international flame retardancystandards. British Standard BS5852 Part 2 1982 entitled “Fire tests forfurniture, Part 2. Methods of test for the ignitability of upholsteredcomposites for seating by flaming sources” describes that in the Crib5test, a wooded crib, made of dry wood stacked in a lattice formationweighing about 17 g, is used as the ignition source and is lowered ontothe test material and ignited with a match. If no flaming or progressivesmouldering is observed on both cover and interior material and flamesself-extinguish within 10 mins, and the mass loss of the test foampieces is less than 60 g, the test is recorded as ‘positive’ and thematerial passes the test. Further details of the test are provided inBritish Standard BS5852 Part 2 1982.

Achieving high surface-softness, high sag value and BS5852 crib 5compliance in a single polyurethane foam is particularly advantageous.

In an embodiment, the polyurethane foam exhibits a mass loss of <50 gduring the BS5852 Crib5 test. Suitably, the polyurethane foam exhibits amass loss of <40 g during the BS5852 Crib5 test. More suitably, thepolyurethane foam exhibits a mass loss of <36 g during the BS5852 Crib5test.

In an embodiment, the polyurethane foam is as defined in any one ofnumbered paragraphs (31)-(51) below:

-   -   31) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 33-80,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   32) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 33-80,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   33) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 40-70,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   34) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 40-55,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   35) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 33-80,        -   an IFD65% value of 70-95, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   36) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 33-80,        -   an IFD65% value of 72-85, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   37) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 33-80,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   38) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 40-70,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   39) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 40-55,        -   an IFD65% value of 50-115, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   40) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 33-80,        -   an IFD65% value of 70-95, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   41) the polyurethane foam has:        -   an IFD25% value of 10-40,        -   an IFD40% value of 33-80,        -   an IFD65% value of 72-85, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   42) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 40-70,        -   an IFD65% value of 70-95, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   43) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 40-55,        -   an IFD65% value of 72-85, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.5.    -   44) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 40-70,        -   an IFD65% value of 70-95, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   45) the polyurethane foam has:        -   an IFD25% value of 20-30,        -   an IFD40% value of 40-55,        -   an IFD65% value of 72-85, and        -   the IFD25% and IFD65% values are such that the sag value is            3.1-3.4.    -   46) the polyurethane foam has:        -   an IFD25% value of 20-24,        -   an IFD40% value of 33-37,        -   an IFD65% value of 70-74, and        -   the IFD25% and IFD65% values are such that the sag value is            3.2-3.4.    -   47) the polyurethane foam has:        -   an IFD25% value of 27-32,        -   an IFD40% value of 41-45,        -   an IFD65% value of 89-93, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.3.    -   48) the polyurethane foam has:        -   an IFD25% value of 37-42,        -   an IFD40% value of 60-64,        -   an IFD65% value of 108-112, and        -   the IFD25% and IFD65% values are such that the sag value is            2.8-2.9.    -   49) the polyurethane foam has:        -   an IFD25% value of 22-27,        -   an IFD40% value of 39-43,        -   an IFD65% value of 75-80, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.4.    -   50) the polyurethane foam has:        -   an IFD25% value of 24-26,        -   an IFD40% value of 39-43,        -   an IFD65% value of 76-79, and        -   the IFD25% and IFD65% values are such that the sag value is            3.0-3.2.    -   51) the polyurethane foam has:        -   an IFD25% value of 22-25,        -   an IFD40% value of 39-42,        -   an IFD65% value of 78-81, and        -   the IFD25% and IFD65% values are such that the sag value is            3.3-3.4.

In an embodiment, the polyurethane foam is as defined in any one ofnumbered paragraphs (31)-(51), and the foam has a density of 35-60kg/m³. Suitably, the foam has a density of 40-60 kg/m³. More suitably,the foam has a density of 40-55 kg/m³.

In an embodiment, the polyurethane foam is as defined in any one ofnumbered paragraphs (31)-(51), and the foam has a ball resilienceof >60% (e.g. 60-75%).

In an embodiment, the polyurethane foam is as defined in any one ofnumbered paragraphs (31)-(51), and the foam exhibits BS5852 Crib5 fireretardancy. Suitably, the polyurethane foam exhibits a mass loss of <50g during the BS5852 Crib5 test. More suitably, the polyurethane foamexhibits a mass loss of <40 g during the BS5852 Crib5 test. Mostsuitably, the polyurethane foam exhibits a mass loss of <36 g during theBS5852 Crib5 test.

In any of the embodiments based on numbered paragraphs (31)-(51), thepolyurethane foam comprises a polyurethane formed by the reaction of atleast one polyol having a molecular weight of 6,000-12,000 Da and an OHfunctionality of 2-4 with at least one methylene diphenyl diisocyanatehaving an NCO content of 26-33%. Suitably, the polyol and methylenediphenyl diisocyanate have any of those definitions discussedhereinbefore in respect of the first aspect of the invention.

In any of the embodiments based on numbered paragraphs (31)-(51), thepolyurethane foam is obtainable by the process defined in any ofnumbered paragraphs (1)-(31) discussed hereinbefore in respect of thefirst aspect of the invention.

Foam Applications

As described hereinbefore, the present invention also provides anarticle comprising a polyurethane foam according to the second or thirdaspect of the invention.

The unique load bearing characteristics of the foams of the presentinvention make them ideally suited to a variety of applicationsrequiring not only firmness and support, but also surface softness andsmoothness.

In an embodiment, the article is a pillow, cushion, mattress, mattresstopper, sofa, chair, seat or footwear insole.

The following numbered clauses (1)-(49) are not claims, but insteaddefine particular aspects and embodiments of the invention:

-   -   1. A process for the preparation of a polyurethane foam, the        process comprising the steps of:        -   a) mixing together the following ingredients in the amounts            specified:            -   i. at least one polyol having an average molecular                weight of 6,000-12,000 Da, wherein the polyol has an OH                functionality of 2-4,            -   ii. at least one methylene diphenyl diisocyanate having                an NCO content of 26-33%, wherein the amount of                diisocyanate relative to the amount of polyol is                sufficient to give an ISO index of 65-90,            -   iii. at least one surfactant in an amount of 0.4-1.0 per                hundred parts polyol,            -   iv. at least one amine catalyst in an amount of 0.1-0.6                per hundred parts polyol, and            -   v. water in an amount of 1.5-4.0 per hundred parts                polyol;        -   b) curing the mixture resulting from step a).    -   2. The process of clause 1, wherein the ingredients specified in        step a) are mixed at a speed of 2,000-8,000 rpm, preferably        4,000-6,000 rpm.    -   3. The process of clause 1 or 2, wherein the polyol has a        molecular weight of 7,000-9,000 Da.    -   4. The process of any preceding clause, wherein the polyol has        an OH functionality of 2.8-3.2.    -   5. The process of any preceding clause, wherein the methylene        diphenyl diisocyanate is a modified methylene diphenyl        diisocyanate.    -   6. The process of any preceding clause, wherein the methylene        diphenyl diisocyanate has an NCO content of 28-33%.    -   7. The process of any preceding clause, wherein the amount of        methylene diphenyl diisocyanate relative to the amount of polyol        is sufficient to give an ISO index of 70-80.    -   8. The process of any preceding clause, wherein in step a), the        surfactant is present in an amount of 0.4-0.8 per hundred parts        polyol.    -   9. The process of any preceding clause, wherein the amine        catalyst is suitable for enhancing the nucleophilicity of the        polyol.    -   10. The process of any preceding clause, wherein the amine        catalyst is triethylene diamine.    -   11. The process of any preceding clause, wherein in step a), the        amine catalyst is present in an amount of 0.2-0.4 per hundred        parts polyol.    -   12. The process of any preceding clause, wherein in step a),        water is present in an amount of 2.0-3.5 per hundred parts        polyol.    -   13. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise at least one flame        retardant in an amount of 3.0-20.0 per hundred parts polyol.    -   14. The process of clause 13, wherein the flame retardant is        present in an amount of 3.0-15.0 per hundred parts polyol,        preferably 4.0-10.0 per hundred parts polyol.    -   15. The process of clause 13 or 14, wherein the flame retardant        is a chlorinated phosphate ester, a halogen-free phosphate        ester, or a mixture thereof.    -   16. The process of clause 13, 14 or 15, wherein those        ingredients mixed in step a) further comprise at least one flame        retardant synergist in an amount of 8.0-20.0, preferably        8.0-15.0, per hundred parts polyol.    -   17. The process of clause 16, wherein the flame retardant        synergist is melamine-based.    -   18. The process of clause 16 or 17, wherein the flame retardant        synergist is melamine.    -   19. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise at least one tin        catalyst in an amount of 0.01-0.2, preferably 0.01-0.1, per        hundred parts polyol.    -   20. The process of clause 19, wherein the tin catalyst is a mild        Lewis acid.    -   21. The process of clause 19 or 20, wherein the tin catalyst is        an alkyl carboxylate.    -   22. The process of any one of clause 19, 20 or 21, wherein the        tin catalyst is stannous octoate.    -   23. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise at least one of a        chain extender and a cross-linker in an amount of 0.2-1.5,        preferably 0.6-1.2, per hundred parts polyol.    -   24. The process of clause 23, wherein the chain extender and/or        cross-linker is diethanol amine.    -   25. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise at least one cell        opener in an amount of 1.0-5.0, preferably 2.0-4.0, per hundred        parts polyol.    -   26. The process of clause 25, wherein the cell opener is a        polyol-based compound.    -   27. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise at least one        blowing agent in an amount of 3.0-10.0, preferably 6.0-8.0, per        hundred parts polyol.    -   28. The process of clause 27, wherein the blowing agent is        methylene chloride.    -   29. The process of any preceding clause, wherein those        ingredients mixed in step a) further comprise a pigment.    -   30. The process of any preceding clause, wherein in step b), the        mixture resulting from step a) is cured in an atmosphere of air.    -   31. The process of any preceding clause, wherein in step b), the        mixture resulting from step a) is cured at a temperature of        15-40° C. and a pressure of 0.9 to 1.1 bar.    -   32. The process of any preceding clause, wherein the process is        a continuous process.    -   33. The process of clause 32, wherein in step a), the polyol is        fed to a mixer at a rate of 100-140 kg/min, preferably 110-130        kg/min.    -   34. The process of clause 32 or 33, wherein in step a), the        methylene diphenyl diisocyanate is fed to a mixer at a rate of        30-80 kg/min, preferably 40-60 kg/min.    -   35. The process of clause 32, 33 or 34, wherein in step a), the        surfactant is fed to a mixer at a rate of 45-85 kg/min,        preferably 55-75 kg/min.    -   36. The process of any one of clause 32 to 35, wherein in step        a), the amine catalyst is fed to a mixer at a rate of 20-50        kg/min, preferably 30-40 kg/min.    -   37. The process of any one of clause 32 to 36, wherein in step        a), water is fed to a mixer at a rate of 2-6 kg/min, preferably        3-5 kg/min.    -   38. A polyurethane foam obtainable by the process of any        preceding clause.    -   39. A polyurethane foam having a sag value of 2.8-3.5, wherein        the sag value is calculated according to the following        expression:

${{Sag}{value}} = \frac{{IFD}65\%}{{IFD}25\%}$

-   -   -   and wherein IFD65% and IFD25% values are determined            according to the protocol set forth in ISO 2439:2008.

    -   40. The polyurethane foam of clause 38 or 39, wherein the        polyurethane foam has a sag value of 3.1-3.4.

    -   41. The polyurethane foam of any one of clause 38, 39 or 40,        wherein the polyurethane foam has an IFD25% value of 10-40,        preferably 20-30, wherein the IFD25% value is determined        according to the protocol set forth in ISO 2439:2008.

    -   42. The polyurethane foam of any one of clause 38 to 41, wherein        the polyurethane foam has an IFD40% value of 20-50, preferably        30-40, wherein the IFD40% value is determined according to the        protocol set forth in ISO 2439:2008.

    -   43. The polyurethane foam of any one of clause 38 to 42, wherein        the polyurethane foam has an IFD65% value of 50-100, preferably        60-90, wherein the IFD65% value is determined according to the        protocol set forth in ISO 2439:2008.

    -   44. The polyurethane foam of any one of clause 38 to 43, wherein        the polyurethane foam has a density of 40-60 kg/m³, preferably        45-50 kg/m³.

    -   45. The polyurethane foam of any one of clause 38 to 44, wherein        the polyurethane foam comprises a polyurethane formed by the        reaction of at least one polyol having a molecular weight of        6,000-12,000 Da and an OH functionality of 2-4 with at least one        methylene diphenyl diisocyanate having an NCO content of 26-33%.

    -   46. The polyurethane foam of any one of clause 38 to 45, wherein        the polyurethane foam comprises one or more of a chlorinated        phosphate ester and a halogen-free phosphate ester fire        retardant, or a residue thereof.

    -   47. The polyurethane foam of any one of clause 38 to 46, wherein        the polyurethane foam exhibits BS5852 Crib5 fire retardancy.

    -   48. An article comprising a polyurethane foam according to any        one of clause 38 to 47.

    -   49. The article of clause 48, wherein the article is a pillow,        cushion, mattress, mattress topper, sofa, chair, seat or        footwear insole.

EXAMPLES

One or more examples of the invention will now be described, for thepurpose of illustration only, with reference to the accompanyingfigures, in which:

FIG. 1 shows a continuous foam forming process used in the preparationof the foams of the examples and comparative examples. The processparameters were: mixing head pressure—0.3 MPa; air injection—0.1 L/min;raw materials temperature—22° C.; foaming speed—4.0 m/min; mixing headmixing speed—5000 rpm.

FIG. 2 shows a box foaming (discontinuous) process.

MATERIALS AND METHODS

In following examples, the components used were:

Polyol A: Caradol SC56-02 (560H value, 3000 mwt.), available from ShellChemicals Company;

Polyol B: GLR2000 (2400H value, 700 mwt.), available from SinopecShanghai Gaoqiao Chemical Company;

Active Polyol C: polyol 330N (330H value 5000 mwt), available fromSinopec Shanghai Gaoqiao Chemical Company;

Active polyol D: polyol GEP828 (28 OH value 8000 mwt) from SinopecShanghai Gaoqiao Chemical Company;

Flame retardant FR508, available from Yoke Chemicals Company;

Flame retardant synergist: melamine;

Surfactant A: B2470, available from Evonik;

Amine catalyst: Niax A1 (available from Momentive) and Dabco 33-LV(available from Air product);

Tin Catalyst: K29 from Enovik;

Toluene diisocyanate (TDI) is available from BASF;

Modified methylene diphenyl diisocyanate (MDI) 6510, available fromHuntsmen Chemicals Company (NCO % 29.9);

Surfactant B: B8002, available from Evonik;

Surfactant L5333 from Momentive;

Cell opener: PK101, available from Fushun Chemical Company;

Cell opener: KZ28, available from Nanjing Aosai Chemical Co.

Blow agent: Methylene chloride;

Chain extender/cross linker: Diethanol amine.

In the following examples, foams were prepared using the continuousfoaming process depicted in FIG. 1 .

Example 1

Having regard to Table 1 below, a flexible polyurethane foam wasprepared according to the continuous foaming process depicted in FIG. 1using the ingredients and amounts specified.

TABLE 1 Ingredients used in the preparation of flexible polyurethanefoam of Example 1 Flow rate to mixer Ingredients Parts/php* head(kg/min) Active polyol D 100  120 Flame retardant FR 508 7 8.4 Melamine10  12 H₂O   3.2 3.84 Methylene chloride 7 8.4 Surfactant L5333   0.550.66 Amine catalyst   0.3 0.36 Tin Catalyst   0.03 0.04 Cell openingagent 3 3.6 Diethanol amine   0.8 0.96 Modified MDI  40** 48 *perhundred parts polyol; **amount of MDI was sufficient to give an ISOindex of 75.

After forming, the foam was left to cure at room temperature for 72hours.

The properties (density, sag value and fire retardancy) of the curedflexible polyurethane foam of Example 1 were then assessed. The resultsare presented in Table 2 below.

TABLE 2 Density, sag value and fire retardancy properties of flexiblepolyurethane foam of Example 1 Foam density (kg/m³) 45 IFD25%/N 22.1IFD40%/N 34.8 IFD65%/N 72.2 Sag value (IFD65%/IFD25%) 3.3 BS5852 crib5fire retardancy Pass, 34 g mass loss

As can be seen from the data presented in Table 2, the IFD25% of theflexible polyurethane foam of Example 1 is 22.1N, which is substantiallylower than that observed for conventional, HR and visco-elasticpolyurethane foams. This value reflects the high surface softness andsmoothness of the flexible polyurethane foam of Example 1 when comparedwith other polyurethane foams. However in spite of the high surfacesoftness and smoothness, the data presented in Table 2 illustrate thatthe sag value of the flexible polyurethane foam—which is typically usedto gauge the level of comfort offered by a foam—is 3.3, which is notablyhigher than that observed for conventional, HR and visco-elasticpolyurethane foams. This means that the foam of Example 1, despitehaving excellent surface softness and smoothness characteristics, alsooffers remarkable support, without excessive sinking. This is likely dueto the fact that whilst the upper surface of the foam is soft, thefirmness of the foam increases sharply upon continued application ofpressure.

In addition to the above, the flexible polyurethane foam of Example 1meets the BS5852 crib 5 flammability standard—a UK requirement which isperhaps the most stringent of all international flame retardancystandards. Achieving high surface-softness, high sag value and BS5852crib 5 compliance in a single polyurethane foam is particularlyadvantageous.

Comparative Example 2—Conventional Flame-Retardant Polyurethane Foam

Having regard to Table 3 below, a flexible conventional flame-retardantpolyurethane foam was prepared according to the continuous foamingprocess depicted in FIG. 1 using the ingredients and amounts specified.

TABLE 3 Ingredients used in the preparation of flexible polyurethanefoam of Comparative Example 2 Flow rate to mixer Ingredients Parts/php*head (kg/min) Polyol, A 100 150 Flame retardant FR508 15 22.5 Melamine30 45 H₂O 3.2 4.8 Methylene chloride 3 4.5 Surfactant A 1.2 1.8 Aminecatalyst 0.3 0.45 Tin Catalyst 0.24 0.36 TDI (NCO %: 48.3) 45.6** 68.4*per hundred parts polyol; **amount of TDI was sufficient to give an ISOindex of 115.

After forming, the foam was left to cure at room temperature for 72hours.

The properties (density, sag value and fire retardancy) of the curedflexible polyurethane foam of Comparative Example 2 were then assessed.The results are presented in Table 4 below.

TABLE 4 Density, sag value and fire retardancy properties of flexiblepolyurethane foam of Comparative Example 1 Foam density (kg/m³) 32IFD25%/N 85.5 IFD40%/N 123.2 IFD65%/N 189.5 Sag value (IFD65%/IFD25%)2.2 BS5852 crib5 Pass, 32 g mass loss

The foam of Comparative Example 2 is a typical BS5852 Crib5-compliantconventional polyurethane foam. Despite being fire retardant, theconventional polyurethane foam of Comparative Example 2 has an extremelyhigh IFD25% value, which manifests itself as poor surface softnesscharacteristics. As a consequence, the foam of Comparative Example 2 isonly suitable for use as a base layer in mattresses, and cannot be usedin the upper surface on which a consumer sleeps.

Comparative Example 3—Visco-Elastic Polyurethane Foam

Having regard to Table 5 below, a flexible polyurethane visco-elasticfoam was prepared according to the continuous foaming process depictedin FIG. 1 using the ingredients and amounts specified.

TABLE 5 Ingredients used in the preparation of flexible polyurethanefoam of Comparative Example 3 Flow rate to mixer Ingredients Parts/php*head (kg/min) Polyol A 50 75 Polyol B 50 75 H₂O 2 3 Surfactant B 0.8 1.2Amine catalyst 0.4 0.6 Tin Catalyst 0.08 0.12 cell open agent 4 6 TDI(NCO %: 48.3) 37.2** 55.8 *per hundred parts polyol; **amount of TDI wassufficient to give an ISO index of 88.

After forming, the foam was left to cure at room temperature for 72hours.

The properties (density, sag value and fire retardancy) of the curedflexible polyurethane visco-elastic foam of Comparative Example 3 werethen assessed. The results are presented in Table 6 below.

TABLE 6 Density, sag value and fire retardancy properties of flexiblepolyurethane foam of Comparative Example 3 Foam density (kg/m³) 43IFD25%/N 30.4 IFD40%/N 43.6 IFD65%/N 60.2 Sag value (IFD65%/IFD25%) 2.0BS5852 crib5 Fail, burnt out

The foam of Comparative Example 3 is a visco-elastic foam that is widelyused in pillows, mattresses and mattress toppers. Although visco-elasticfoams offer softness and are able to conform to the body in order todistribute body pressure evenly, they suffer from the standpoint ofproviding sufficient support. As can be seen from the data presented inTable 6, sag value of the visco-elastic foam of Comparative Example 3 isonly 2.0, which translates to a consumers feeling that they are sunkeninto the foam, rather than being properly supported by it.

Comparative Example 4—Flame-Retardant HR Polyurethane Foam

Having regard to Table 7 below, a flexible polyurethane HR foam wasprepared according to the continuous foaming process depicted in FIG. 1using the ingredients and amounts specified.

TABLE 7 Ingredients used in the preparation of flexible polyurethanefoam of Comparative Example 4 Flow rate to mixer Ingredients Parts/phphead (kg/min)* Active polyol C 100 150 Flame retardant 8 12 Melamine 1518 H₂O 3 4.5 Methylene chloride 3 4.5 Surfactant C 0.6 0.9 Aminecatalyst 0.3 0.45 Tin Catalyst 0.1 0.15 Diethanol amine 1 1.5 TDI (NCO%: 48.3) 40.2** 60.3 *per hundred parts polyol; **amount of TDI wassufficient to give an ISO index of 110.

After forming, the foam was left to cure at room temperature for 72hours.

The properties (density, sag value and fire retardancy) of the curedflexible polyurethane HR foam of Comparative Example 4 were thenassessed. The results are presented in Table 8 below.

TABLE 8 Density, sag value and fire retardancy properties of flexiblepolyurethane foam of Comparative Example 4 Foam density (kg/m³) 31IFD25%/N 67.4 IFD40%/N 100.5 IFD65%/N 182 Sag value (IFD65%/IFD25%) 2.7BS5852 crib5 Pass, 35 g mass loss

The foam of Comparative Example 4 is a typical BS5852 Crib5-compliant HRpolyurethane foam. The foam exhibits good support properties, due inpart to the higher molecular weight of polyol used in comparison toconventional and visco-elastic foams, which makes the HR foam widelyuseable in the seat portion of chairs and sofas. However, the HRpolyurethane foam of Comparative Example 4 has an extremely high IFD25%value, which manifests itself as poor surface softness characteristics.As a consequence, the foam of Comparative Example 4 is unsuitable foruse in pillows and mattress toppers, wherein high surface-softness isnecessary.

Example 5

Having regard to Tables 9 and 10 below, various polyurethane foams wereprepared according to the continuous foaming process depicted in FIG. 1using the ingredients and amounts specified.

TABLE 9 Composition and properties of various polyurethane foams Foam 12* 3 4* 5 6 FOAM COMPOSITION Active polyol D 100 100 100 100 100 100Cell opener 3 3 3 3 3 5 KZ28/phpp Flame retardant 3 20 12 12 12 0FR508/phpp Melamine/phpp 15 15 15 15 15 0 Silicone 0.7 0.7 0.7 0.7 0.70.7 surfactant L5333/phpp Amine 0.5 0.5 0.5 0.5 0.5 0.5 catalyst/phppTin catalyst/ 0.05 0.05 0.05 0.05 0.05 0.05 phpp H2O/phpp 2 2 4 1 2 2Blow agent/ 5 5 5 5 5 2 phpp TEOA/phpp 0.6 0.6 0.6 0.6 0.6 0.6 ISOindex** 90 90 90 90 90 100 FOAM PROPERTIES Cream time/s 10 12 8 30 10 8Full rising 163 183 125 N/A 172 159 time/s Foam density/ 54.2 60.4 36.3N/A 57.2 55.2 kg/m3 IFD 25/40/ 29/43/91 29.3/41.1/78.2 39.5/62/110.2 N/A25.2/41.3/77.2 23.5/40.3/79.2 65(N) Sag value 3.1 2.67 2.8 N/A 3.1 3.4Ball 62 52 50 N/A 65 69 resilience/% Overall foam 5 2 3 N/A 5 5 physicalperformance (1-5; 1 = poor, 5 = excellent) FR BS5852 crib Fail. Foamcontinued Pass. Mass Fail. Foam continued N/A Pass. Mass Fail. Foamcontinued 5 test burning after 10 mins. loss 38 g burning after 10 mins.loss 35 g burning after 10 mins. Mass loss > 60 g after 4 mins Massloss > 60 g after 4 mins Mass loss > 60 g 35 sec 55 sec Comments Foamexhibits BS5852 crib 5 Higher water Low water BS5852 crib 5 Foamexhibits excellent excellent compliant, but content gave rise contentcompliant physical properties. physical high content of to certaindefects hampered foam and excellent Lack of flame retardant properties.flame retardant in foam, and rising. Sample physical meant foam was notNot enough flame compromised overall poorer not cured properties BS5852crib retardant to confer physical prop- physical 5 compliant BS5852 crib5 erties of foam properties compliance *comparative example; **ISO indexachieved by adding appropriate amount of modified MDI; phpp-per hundredparts polyol

TABLE 10 Composition and properties of various polyurethane foams Foam7* 8* 9* 10* 11* 12* FOAM COMPOSITION Active polyol D 100 100 100 100100 100 Cell opener 3 3 3 3 3 3 KZ28/phpp Flame retardant 12 12 12 12 1212 FR508/phpp Melamine/phpp 15 15 15 15 15 15 Silicone surfactant 0.70.7 0.7 0.7 0.1 2 L5333/phpp Amine 0.1 1 0.5 0.5 0.5 0.5 catalyst/phppTin catalyst/phpp 0.05 0.05 0.05 0.05 0.05 0.05 H2O/phpp 2 2 2 2 2 2Blow agent/phpp 5 5 5 5 5 2 TEOA/phpp 0.6 0.6 0.6 0.6 0.6 0.6 ISOindex** 90 90 70 120 90 90 FOAM PROPERTIES Cream time/s 40 2 16 8 11 10Full rising time/s NA 81 192 150 NA 172 Foam density/ NA NA 65.2 55.2 NANA kg/m3 IFD 25/40/65(N) NA NA 14.2/24.2/45.2 40.4/65.8/110.8 NA NA Sagvalue NA NA 3.2 2.7 NA NA Ball resilience/% NA NA 53 52 NA NA Overallfoam NA 1 2 2 1 1 physical performance (1-5; 1 = poor, 5 = excellent) FRBS5852 NA NA Fail. Foam continued Pass. Mass NA NA crib 5 test burningafter 10 mins. loss 28 g Mass loss > 60 g after 3 mins 56 sec CommentsInsufficient Excessive amount Low ISO index High ISO index Insufficientamount Excessive amount of amount of of amine catalyst resulted inoverly resulted in overly of surfactant led to surfactant led to aminecatalyst caused foam to soft foam having firm foam having larger cells,causing closed cell structure, for foam rise too quickly, poor support aclosed cell foam collapse while causing foam shrinkage to rise causingsplitting characteristics. structure and rising after curing Flameretardancy poor surface also compromised smoothness *comparativeexample; **ISO index achieved by adding appropriate amount of modifiedMDI; phpp-per hundred parts polyol

The results presented in Tables 9 and 10 illustrate the effect ofvarying the amount of the various ingredients of the foam.

While specific embodiments of the invention have been described hereinfor the purpose of reference and illustration, various modificationswill be apparent to a person skilled in the art without departing fromthe scope of the invention as defined by the appended claims.

The invention claimed is:
 1. A process for the preparation of apolyurethane foam, the process comprising the steps of: a) mixingtogether the following ingredients in the amounts specified: i. at leastone polyol having an average molecular weight of 7,500-8,500 Da, whereinthe polyol has an OH functionality of 2-4 and an OH value of 26-30, ii.at least one methylene diphenyl diisocyanate having an NCO content of29-31%, wherein the amount of diisocyanate relative to the amount ofpolyol is sufficient to give an ISO index of 72-110, wherein themethylene diphenyl diisocyanate is a modified methylene diphenyldiisocyanate, iii. at least one surfactant in an amount of 0.5-0.75 perhundred parts polyol, iv. at least one blowing agent in an amount of1.5-8.0 per hundred parts polyol, v. at least one cell opener in anamount of 2.0-5.5 per hundred parts polyol, vi. at least one aminecatalyst in an amount of 0.2-0.55 per hundred parts polyol, vii. atleast one tin catalyst in an amount of 0.01-0.1 per hundred partspolyol, viii. water in an amount of 1.5-3.3 per hundred parts polyol,and ix. optionally at least one flame retardant in an amount of 6.5-14.0per hundred parts polyol, wherein when a flame retardant is used, it isused in conjunction with a melamine-based flame-retardant synergist,wherein the melamine-based flame retardant synergist, when present, ispresent in an amount of 9.0-17.0 per hundred parts polyol; b) curing themixture resulting from step a); wherein, in step a), the polyol is fedto a mixer at a rate of 100-140 kg/min.
 2. The process of claim 1,wherein the ingredients specified in step a) are mixed at a speed of2,000-8,000 rpm.
 3. The process of claim 1, wherein the polyol is apolyether polyol and/or has an OH functionality of 2.8-3.2.
 4. Theprocess of claim 1, wherein the amine catalyst is triethylene diamine.5. The process of claim 1, wherein in step a), the at least one flameretardant is present in an amount of 6.5-14.0 per hundred parts polyol,or the flame retardant is present in an amount of 8.0-13.5 per hundredparts polyol.
 6. The process of claim 1, wherein the tin catalyst is analkyl carboxylate.
 7. The process of claim 1, wherein those ingredientsmixed in step a) further comprise at least one of a chain extender and across-linker in an amount of 0.2-1.5 per hundred parts polyol, and thechain extender and/or cross-linker is diethanol amine.
 8. The process ofclaim 1, wherein in step b), the mixture resulting from step a) is curedin an atmosphere of air.
 9. The process of claim 1, wherein in step a),the polyol is fed to a mixer at a rate of 100-140 kg/min, or themethylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80kg/min, or the surfactant is fed to a mixer at a rate of 45-85 kg/min,or the amine catalyst is fed to a mixer at a rate of 20-50 kg/min, orwater is fed to a mixer at a rate of 2-6 kg/min.
 10. The process ofclaim 1, wherein the process comprises the steps of: a) mixing togetherthe following ingredients in the amounts specified: i. at least onepolyol having an average molecular weight of 7,500-8,500 Da, wherein thepolyol has an OH functionality of 2.8-3.2 and an OH value of 26-30, ii.at least one methylene diphenyl diisocyanate having an NCO content of29-31%, wherein the amount of diisocyanate relative to the amount ofpolyol is sufficient to give an ISO index of 72-100, wherein themethylene diphenyl diisocyanate is a modified methylene diphenyldiisocyanate, iii. at least one surfactant in an amount of 0.55-0.75 perhundred parts polyol, iv. at least one blowing agent in an amount of4.0-8.0 per hundred parts polyol, v. at least one cell opener in anamount of 2.0-5.5 per hundred parts polyol, vi. at least one aminecatalyst in an amount of 0.2-0.55 per hundred parts polyol, vii. atleast one tin catalyst in an amount of 0.01-0.05 per hundred partspolyol, viii. water in an amount of 1.5-3.3 per hundred parts polyol,and ix. at least one of a chain extender and a cross-linker in an amountof 0.6-1.2 per hundred parts polyol, x. optionally at least one flameretardant in an amount of 6.5-14.0 per hundred parts polyol, whereinwhen a flame retardant is used, it is used in conjunction with amelamine-based flame-retardant synergist, wherein the melamine-basedflame retardant synergist, when present, is present in an amount of9.0-17.0 per hundred parts polyol; b) curing the mixture resulting fromstep a) to form a polyurethane foam having a density of 40-60 kg/m³wherein, in step a), the polyol is fed to a mixer at a rate of 110-130kg/min.